Phosphorus-containing oligomer and method for producing the same, curable resin composition and cured product of the same, and printed wiring board

ABSTRACT

Phosphorus-containing oligomer is represented by formula (1): 
                         
(R 1  represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a phenyl group; n is the number of repeating units and an integer of 1 or more; X is a structural unit represented by structural formula (x1) or (x2) below;
 
                         
Y is a hydrogen atom, a hydroxyl group, or a structural unit represented by the formula (x1) or (x2); and, in the formula (x1) or (x2), R 2 , R 3 , R 4 , and R 5  each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or an aralkyl group), wherein the content of components whose n is 2 or more in the formula (1) is in the range of 5% to 90% in peak area in GPC measurement.

This application is a 371 filing of PCT/JP2011/051991, filed Feb. 1,2011

TECHNICAL FIELD

The present invention relates to a phosphorus-containing oligomer thathas high solubility in a solvent and exhibits high flame retardancy andheat resistance in the form of a cured product thereof, a method forproducing the phosphorus-containing oligomer, a curable resincomposition that uses the oligomer as a curing agent for epoxy resins, acured product of the curable resin composition, and a printed wiringboard that uses the curable resin composition.

BACKGROUND ART

Epoxy resins and epoxy resin compositions containing a curing agent forepoxy resins as an essential component have excellent physicalproperties such as high heat resistance and moisture resistance andhence are widely used for, for example, semiconductor sealing materials,electronic components such as printed circuit boards, the electroniccomponent field, conductive adhesives such as conductive pastes, otheradhesives, matrices for composite materials, coating materials,photoresist materials, and development materials.

In recent years, further enhancement of properties such as heatresistance, moisture resistance, and solder resistance has been demandedin such various applications, in particular, applications to advancedmaterials. In vehicle-mounted electronic devices that are particularlyrequired to have high reliability, the installation position has beenchanged from a cabin to an engine compartment having a highertemperature than a cabin. In addition, reflowing treatment temperaturehas increased due to use of lead-free solder. Therefore, high heatresistant materials that have higher glass transition temperature andcan endure a thermal delamination test (hereinafter, abbreviated as“T288 test”) have been demanded.

When epoxy resin compositions are used as materials for printed wiringboards, a flame retardant containing halogen such as bromine is addedtogether with an antimony compound to impart flame retardancy to epoxyresin compositions. However, with efforts in terms of environment andsafety in recent years, there has been a strong demand for thedevelopment of an environmentally friendly and safe method for makingcompositions have flame retardancy without using halogen-based flameretardants that may emit dioxins and without using antimony compoundsthat may cause cancer. In addition, in the field of materials forprinted wiring boards, use of halogen-based flame retardants causesdegradation of reliability of printed wiring boards left to stand athigh temperature. Accordingly, halogen-free compositions have beenhighly demanded.

As for an epoxy resin composition that satisfies such requiredcharacteristics and has flame retardancy and heat resistance, forexample, PTL 1 discloses a technique of using, as an epoxy resinmaterial or a curing agent for epoxy resins, a phosphorus-containingbisphenol that is obtained as follows:9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (hereinafter,abbreviated as “HCA”) is allowed to react with p-hydroxybenzaldehyde andthen the reaction product is allowed to react with phenol.

However, such a phosphorus-containing bisphenol has extremely highcrystallinity and exhibits almost no solubility in a solvent. Therefore,such a phosphorus-containing bisphenol cannot be prepared in the form ofvarnish for the printed wiring board materials, and a cured productobtained by using the phosphorus-containing bisphenol as a curing agentfor epoxy resins does not have satisfactory flame retardancy. Inaddition, since the melting point of the phosphorus-containing bisphenolis 200° C. or more, it is extremely difficult to perform industrialproduction.

NPL 1 discloses a technique of producing an oligomer in THF from anintermediate product obtained through a reaction between HCA andp-hydroxybenzaldehyde.

However, in the technique disclosed in NPL 1, the reaction product ofHCA and p-hydroxybenzaldehyde, which is an intermediate product, hasextremely high crystallinity and thus has low solubility in a solvent.Therefore, as described in NPL 1, THF, which is a dangerous solventhaving a low flash point, needs to be used in the subsequent reactionand thus it is impossible to perform industrial production. In addition,the obtained oligomer itself has low solubility in a solvent and thus itis difficult to prepare a varnish for printed wiring board materials.

Furthermore, PTL 2 discloses a technique of producing aphosphorus-containing phenolic compound through a reaction between HCAand hydroxybenzaldehyde. However, the phenolic compound disclosed in PTL2 is a monofunctional phenolic compound and thus has extremely highcrystallinity and low solubility in a solvent. In addition, even whenthe phenolic compound is used as a curing agent for epoxy resins,sufficient flame retardancy is not achieved.

CITATION LIST Patent Literature

-   PTL 1: Japanese Unexamined Patent Application Publication No.    2004-143166-   PTL 2: Japanese Unexamined Patent Application Publication No.    2001-354685

Non Patent Literature

-   NPL 1: “Flame-retardant epoxy resins from novel    phosphorus-containing novolac”, polymer (polymer 42 (2001) 3445 to    3454), Ying Ling Liu

SUMMARY OF INVENTION Technical Problem

Accordingly, it is an object of the present invention to provide aphosphorus-containing oligomer that has a significantly improvedsolubility in an organic solvent and exhibits high flame retardancy andheat resistance in the form of a cured product thereof, a method forproducing the phosphorus-containing, oligomer with high industrialproductivity, a curable resin composition containing the oligomer and acured product thereof, and a printed wiring board produced from thecomposition.

Solution to Problem

As a result of thorough studies to address the problems above, theinventors of the present invention have found the following and havecompleted the present invention. That is, a phosphorus-containingoligomer obtained through a reaction between a phosphorus-containingcompound such as HCA and o-hydroxybenzaldehyde exhibits high solubilityin an organic solvent. Furthermore, when the oligomer is used as acuring agent for epoxy resins, an epoxy resin material, an additive forthermosetting resins, or the like and curing is performed, the curedproduct exhibits high flame retardancy, has high glass transitiontemperature, and can endure a T288 test.

The present invention relates to a phosphorus-containing oligomerrepresented by structural formula (1) below:

(in the formula, R¹ represents a hydrogen atom, an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or aphenyl group; n is the number of repeating units and an integer of 1 ormore; X is a structural unit represented by structural formula (x1) or(x2) below;

Y is a hydrogen atom, a hydroxyl group, or a structural unit representedby the structural formula (x1) or (x2); and, in the structural formula(x1) or (x2), R², R³, R⁴, and R⁵ each independently represent a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or anaralkyl group), wherein the content of components whose n is 2 or morein the structural formula (1) is in the range of 5% to 90% in terms ofpeak area in GPC measurement.

The present invention also relates to a method for producing aphosphorus-containing oligomer, the method including mixing a compound(a1) represented by structural formula (a1-1) or (a1-2) below and acompound (a2) represented by structural formula (a2) below with eachother at a molar ratio of [compound (a1)/compound (a2)]=0.01/1.0 to0.99/1.0; causing a reaction to proceed at 80° C. to 180° C. in thepresence of an acid catalyst; then adding the compound (a1) so that thetotal amount on a molar basis is 1.01 to 3.0 times the amount of thecompound (a2) charged; and causing a reaction to proceed at 120° C. to200° C.,

(in the formula, R², R³, R⁴, and R⁵ each independently represent ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenylgroup, or an aralkyl group)

(in the formula, R¹ represents a hydrogen atom, an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or aphenyl group).

The present invention also relates to a curable resin composition thatincludes an epoxy resin and a curing agent as essential components,wherein the phosphorus-containing oligomer is used as the curing agent.

The present invention also relates to a cured product obtained by curingthe curable resin composition.

The present invention also relates to a printed wiring board obtained byfurther adding an organic solvent to the curable resin composition toform a resin composition in the form of varnish, impregnating areinforcing base with the resin composition in the form of varnish,laminating a copper foil on the reinforcing base, and performingthermocompression bonding.

Advantageous Effects of Invention

According to the present invention, there can be provided aphosphorus-containing oligomer that has a significantly improvedsolubility in an organic solvent and exhibits high flame retardancy andheat resistance in the form of a cured product thereof, a method forproducing the phosphorus-containing oligomer with high industrialproductivity, a curable resin composition containing the oligomer and acured product thereof, and a printed wiring board produced from thecomposition.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a GPC chart of a phosphorus-containing oligomer (A-1)obtained in Example 1.

FIG. 2 shows a ¹³C-NMR chart of the phosphorus-containing oligomer (A-1)obtained in Example 1.

FIG. 3 shows an MS spectrum of the phosphorus-containing oligomer (A-1)obtained in Example 1.

FIG. 4 shows a GPC chart of a phosphorus-containing oligomer (A-2)obtained in Example 2.

FIG. 5 shows a GPC chart of a phosphorus-containing oligomer (A-3)obtained in Example 3.

FIG. 6 shows a GPC chart of a phosphorus-containing oligomer (A-4)obtained in Example 4.

FIG. 7 shows a GPC chart of a phosphorus-containing oligomer (A-5)obtained in Example 5.

FIG. 8 shows a GPC chart of a phenolic compound (A-6) obtained inSynthetic Comparative Example 1.

FIG. 9 shows a GPC chart of a phenolic resin (A-7) obtained in SyntheticComparative Example 2.

FIG. 10 shows a GPC chart of a phenolic compound (A-8) obtained inSynthetic Comparative Example 3.

DESCRIPTION OF EMBODIMENTS

The present invention will now be described in detail.

As described above, the phosphorus-containing oligomer of the presentinvention is represented by structural formula (1) below:

(in the formula, R¹ represents a hydrogen atom, an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or aphenyl group; n is the number of repeating units and an integer of 1 ormore; X is a structural unit represented by structural formula (x1) or(x2) below;

Y is a hydrogen atom, a hydroxyl group, or a structural unit representedby the structural formula (x1) or (x2); and, in the structural formula(x1) or (x2), R², R³, R⁴, and R⁵ each independently represent a hydrogenatom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or anaralkyl group). The content of components whose n is 2 or more in thestructural formula (1) is in the range of 5% to 90% in terms of peakarea in GPC measurement.

The phosphorus-containing oligomer includes, as a repeating unit, astructural unit represented by structural formula (2) below in thestructural formula (1):

(in the formula, R¹ represents a hydrogen atom, an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or aphenyl group; n is the number of repeating units and an integer of 1 ormore; and X is a structural unit represented by structural formula (x1)or (x2) below).

Therefore, the cured product of the phosphorus-containing oligomer hashigh flame retardancy, high glass transition temperature, and highthermal delamination resistance.

Specific examples of the structural unit represented by the structuralformula (2) include structural units represented by structural formulae(2-1) to (2-8) below.

In the present invention, X in the structural formula (1) is selectedfrom the structural units represented by the structural formulae (x1)and (x2), but is particularly preferably the structural unit representedby the structural formula (x1) in view of flame retardancy. Therefore,among the structural units represented by the structural formula (2), Xis preferably selected from the structural units represented by thestructural formulae (2-1), (2-2), (2-3), and (2-4) that each correspondto the structural formula (x-1).

In the structural formula (1), Y is a hydrogen atom, a hydroxyl group,or a structural unit represented by the structural formula (x1) or (x2),but they may be present together in the phosphorus-containing oligomer.In the present invention, Y is preferably a hydrogen atom or thestructural unit represented by the structural formula (x1) or (x2) inview of solubility in a solvent and heat resistance and particularlypreferably the structural unit represented by the structural formula(x1) in view of flame retardancy.

As described above, in the phosphorus-containing oligomer, the contentof components whose n is 2 or more in the structural formula (1) is inthe range of 5% to 90% in terms of peak area in GPC measurement. Whenthe content is in the range, the solubility of the oligomer in anorganic solvent and the flame retardancy of a cured product aresignificantly improved.

Herein, the phrase “the content of components whose n is 2 or more inthe structural formula (1)” means a peak area percentage before 36.0minutes in a GPC chart measured under the following conditions.

<GPC Measurement Conditions>

4) GPC: the measurement conditions are as follows.

Measurement apparatus: “HLC-8220 GPC” manufactured by Tosoh Corporation

Columns: guard column “HXL-L” manufactured by Tosoh Corporation,

+“TSK-GEL G2000HXL” manufactured by Tosoh Corporation,

+“TSK-GEL G2000HXL” manufactured by Tosoh Corporation,

+“TSK-GEL G3000HXL” manufactured by Tosoh Corporation,

+“TSK-GEL G4000HXL”, manufactured by Tosoh Corporation

Detector: RI (differential refractive refractometer)

Data processing: “GPC-8020 Model II version 4.10” manufactured by TosohCorporation

Measurement conditions: column temperature 40° C. developing solventtetrahydrofuran flow rate 1.0 ml/min

Standards: the following monodisperse polystyrenes whose molecularweights are known were used in accordance with the measurement manual ofthe “GPC-8020 Model II version 4.10”

(Used polystyrenes)

“A-500” manufactured by Tosoh Corporation

“A-1000” manufactured by Tosoh Corporation

“A-2500” manufactured by Tosoh Corporation

“A-5000” manufactured by Tosoh Corporation

“F-1” manufactured by Tosoh Corporation

“F-2” manufactured by Tosoh Corporation

“F-4” manufactured by Tosoh Corporation

“F-10” manufactured by Tosoh Corporation

“F-20” manufactured by Tosoh Corporation

“F-40” manufactured by Tosoh Corporation

“F-80” manufactured by Tosoh Corporation

“F-128” manufactured by Tosoh Corporation

Samples: solutions (50 μl) obtained by filtrating a 1.0 mass %tetrahydrofuran solution in terms of resin solid matter through amicro-filter.

5) NMR: JNM-ECA500 nuclear magnetic resonance apparatus manufactured byJEOL Ltd.

Magnetic field strength: 500 MHz

Pulse width: 3.25 μsec

Number of acquisitions: 8000

Solvent: DMSO-d6

Sample concentration: 30 wt %

6) MS: AXIMA-TOF2 manufactured by SHIMADZU BIOTECH

Measurement mode: linear

Number of acquisitions: 50

Sample composition: sample/DHBA/NaTFA/THF=9.4 mg/104.7 mg/6.3 mg/1 ml

In the present invention, when the content of components whose n is 2 ormore is 5% or more in terms of peak area in GPC measurement, thesolubility in a solvent is improved. When the content is 90% or less,the liquidity in a molten state or the liquidity in the form of varnishis improved. Herein, the other component is a component whose n is 1.Thus, in the phosphorus-containing oligomer of the present invention,the content of a component whose n is 1 is 95% to 10% in terms of peakarea in GPC measurement. In the present invention, the content ofcomponents whose n is 2 or more is preferably 40% to 75% and the contentof a component whose n is 1 is preferably 60% to 25% to maintain thesolubility in a solvent and the fluidity and to achieve high heatresistance, in particular, to achieve high glass transition temperatureand high performance in a T288 test.

More specifically, preferably, the content of a component whose n is 1is 95% to 10%, the content of a component whose n is 2 is 3% to 50%, andthe content of components whose n is 3 or more is 1% to 45% in view ofsolubility in a solvent. Particularly preferably, the content of acomponent whose n is 1 is 60% to 25%, the content of a component whose nis 2 is 10% to 45%, and the content of components whose n is 3 or moreis 10% to 40% in view of good balance of solubility in a solvent,liquidity, and heat resistance.

As described above, Y in the structural formula (1) is preferably astructural unit represented by the structural formula (x1). Therefore, aphosphorus-containing oligomer in which, in the structural formula (1),Y is a structural unit represented by the structural formula (x1), thecontent of components whose n is 2 or more is 40% to 75%, and thecontent of a component whose n is 1 is 60% to 25% is preferably employedin view of flame retardancy and heat resistance. A phosphorus-containingoligomer in which, in the structural formula (1), Y is a structural unitrepresented by the structural formula (x1), the content of a componentwhose n is 1 is 95% to 10%, the content of a component whose n is 2 is3% to 50%, and the content of components whose n is 3 or more is 1% to45% is more preferably employed in view of high flame retardancy, heatresistance, and solubility in a solvent. A phosphorus-containingoligomer in which Y is a structural unit represented by the structuralformula (x1), the content of a component whose n is 1 is 60% to 25%, thecontent of a component whose n is 2 is 10% to 45%, and the content ofcomponents whose n is 3 or more is 10% to 40% is most preferablyemployed in view of good balance of flame retardancy, solubility in asolvent, liquidity, and heat resistance.

In the phosphorus-containing oligomer, the content of phosphorus in theoligomer is preferably 9% to 12% by mass in view of flame retardancy.The content of phosphorus is measured in conformity with “JIS K0102 46”.

The phosphorus-containing oligomer described in detail is preferably aphosphorus-containing oligomer produced by the following productionmethod of the present invention to achieve high solubility in an organicsolvent and high heat resistance of a cured product.

As described above, the production method of the present inventionincludes mixing a compound (a1) represented by structural formula (a1-1)or (a1-2) below and a compound (a2) represented by structural formula(a2) below with each other at a molar ratio of [compound (a1)/compound(a2)]=0.01/1.0 to 0.99/1.0; causing a reaction to proceed at 80° C. to180° C. in the presence of an acid catalyst; then adding the compound(a1) so that the total amount on a molar basis is 1.01 to 3.0 times theamount of the compound (a2) charged; and causing a reaction to proceedat 120° C. to 200° C.

(In the formula, R², R³, R⁴, and R⁵ each independently represent ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenylgroup, or an aralkyl group.)

(In the formula, R¹ represents a hydrogen atom, an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or aphenyl group)

In the present invention, when a phosphorus-containing oligomer isproduced by the method above, the precipitation of a reactionintermediate can be favorably reduced and higher molecular weight iseasily achieved.

Examples of the alkyl group having 1 to 5 carbon atoms that constitutesR², R³, R⁴, and R⁵ in the structural formula (a1-1) or (a1-2) include amethyl group, an ethyl group, an n-propyl group, an i-propyl group, anda t-butyl group. However, in the compound (a1) used in the presentinvention, R², R³, R⁴, and R⁵ are each preferably a hydrogen atom inview of flame retardancy. Furthermore, the compound (a1) is preferablyrepresented by the structural formula (a1-1) in view of high flameretardancy of a cured product. In the compound (a2), examples of R¹ inthe structural formula (a2) include a methyl group, an ethyl group, ann-propyl group, and a methoxy group, but R¹ is preferably a hydrogenatom in view of the reactivity with the compound (a1) and high flameretardancy of a cured product.

Examples of the catalyst that can be used in the method includeinorganic acids such as hydrochloric acid, sulfuric acid, and phosphoricacid; organic acids such as methanesulfonic acid, p-toluenesulfonicacid, and oxalic acid; and Lewis acids such as boron trifluoride,anhydrous aluminum chloride, and zinc chloride. The amount of such acatalyst used is preferably 0.1% to 5.0% by mass relative to the totalweight of charged raw materials in order to prevent a decrease inelectrical insulation of a cured product.

Since the compound (a2) is liquid, the reaction can be caused to proceedusing the compound (a2) as an organic solvent. However, other organicsolvents may be used to improve the work efficiency or the like. Theorganic solvent may be a non-ketonic organic solvent such as an alcoholorganic solvent or a hydrocarbon organic solvent. Specifically, thealcohol organic solvent may be propylene glycol monomethyl ether and thehydrocarbon organic solvent may be toluene or xylene.

After the reaction, an intended product can be obtained by performingdrying under reduced pressure.

The curable resin composition of the present invention is a curableresin composition including an epoxy resin and a curing agent asessential components, and the phosphorus-containing oligomer of thepresent invention is used as the curing agent.

The epoxy resin used herein may be various epoxy resins. Examples of theepoxy resin include bisphenol epoxy resins such as a bisphenol A epoxyresin and a bisphenol F epoxy resin; biphenyl epoxy resins such as abiphenyl epoxy resin and a tetramethyl biphenyl epoxy resin; novolacepoxy resins such as a phenolic novolac epoxy resin, a cresol novolacepoxy resin, a bisphenol A novolac epoxy resin, epoxidized condensatesderived from a phenol and an aromatic aldehyde having a phenolichydroxyl group, and a biphenyl novolac epoxy resin; triphenylmethaneepoxy resins; tetraphenylethane epoxy resins; dicyclopentadiene-phenoladdition reaction epoxy resins; phenol aralkyl epoxy resins; epoxyresins intramolecularly having a naphthalene skeleton, such as anaphthol novolac epoxy resin, a naphthol aralkyl epoxy resin, anaphthol-phenol cocondensation novolac epoxy resin, a naphthol-cresolcocondensation novolac epoxy resin, diglycidyloxynaphthalene, and1,1-bis(2,7-diglycidyloxy-1-naphthyl)alkane; and phosphorus-containingepoxy resins. These epoxy resins may be used alone or in combination oftwo or more thereof.

Examples of the phosphorus-containing epoxy resin include epoxidizedproducts of a phenolic resin obtained through a reaction between9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (hereinafter,abbreviated as “HCA”) and a quinone, epoxy resins obtained by modifyinga phenolic novolac epoxy resin with HCA, epoxy resins obtained bymodifying a cresol novolac epoxy resin with HCA, epoxy resins obtainedby modifying a bisphenol A epoxy resin with a phenolic resin obtainedthrough a reaction between HCA and a quinone, and epoxy resins obtainedby modifying a bisphenol F epoxy resin with a phenolic resin obtainedthrough a reaction between HCA and a quinone.

Among the above-described epoxy resins, novolac epoxy resins and epoxyresins having a naphthalene skeleton in the molecular structure areparticularly preferred in view of heat resistance; and bisphenol epoxyresins and novolac epoxy resins are preferred in view of solubility in asolvent.

The amounts of the epoxy resin and the phosphorus-containing oligomer inthe curable resin composition of the present invention are notparticularly limited. The amounts are preferably set such that theamount of active hydrogen in the phosphorus-containing oligomer is 0.7to 1.5 equivalents per equivalent of epoxy groups in total of the epoxyresin because a cured product to be obtained has good characteristics.

In the curable resin composition of the present invention, a curingagent other than the phosphorus-containing oligomer may be used as thecuring agent for epoxy resins so long as the advantages of the presentinvention are not impaired. Such another curing agent may be an aminecompound, an amide compound, an acid anhydride compound, a phenoliccompound, or the like. Specific examples of the amine compound includediaminodiphenylmethane, diethylenetriamine, triethylenetetramine,diaminodiphenyl sulfone, isophoronediamine, imidazole, BF₃-aminecomplexes, and guanidine derivatives. Specific examples of the amidecompound include dicyandiamide and polyamide resins synthesized from adimer of linolenic acid and ethylenediamine. Specific examples of theacid anhydride compound include phthalic anhydride, trimelliticanhydride, pyromellitic dianhydride, maleic anhydride,tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride,methylnadic anhydride, hexahydrophthalic anhydride, andmethylhexahydrophthalic anhydride. Specific examples of the phenoliccompound include polyhydric phenolic compounds such as a phenolicnovolac resin, a cresol novolac resin, an aromatic hydrocarbonformaldehyde resin-modified phenolic resin, a dicyclopentadiene-phenoladduct resin, a phenol aralkyl resin (Xylok resin), naphthol aralkylresin, a trisphenylolmethane resin, a tetraphenylolethane resin, anaphthol novolac resin, a naphthol-phenol cocondensation novolac resin,a naphthol-cresol cocondensation novolac resin, a biphenyl-modifiedphenolic resin (a polyhydric phenolic compound in which phenolic nucleiare bonded to each other through bismethylene groups), abiphenyl-modified naphthol resin (a polyhydric naphthol compound inwhich phenolic nuclei are bonded to each other through bismethylenegroups), an aminotriazine-modified phenolic resin (a compoundintramolecularly having a phenolic skeleton, a triazine ring, and aprimary amino group), and an alkoxy-group-containing aromatic ringmodified novolac resin (a polyhydric phenolic compound in which phenolicnuclei and alkoxy-group-containing aromatic rings are bonded to eachother through formaldehyde).

Among these compounds, compounds intramolecularly having a large numberof aromatic skeletons are particularly preferred in view of excellentlow thermal expansion of a cured product. Specifically, in view ofexcellent low thermal expansion, preferred examples of the compoundsinclude a phenolic novolac resin, a cresol novolac resin, an aromatichydrocarbon formaldehyde resin-modified phenolic resin, a phenol aralkylresin, a naphthol aralkyl resin, a naphthol novolac resin, anaphthol-phenol cocondensation novolac resin, a naphthol-cresolcocondensation novolac resin, a biphenyl-modified phenolic resin, abiphenyl-modified naphthol resin, an aminotriazine-modified phenolicresin, and an alkoxy-group-containing aromatic ring modified novolacresin (a polyhydric phenolic compound in which phenolic nuclei andalkoxy-group-containing aromatic rings are bonded to each other throughformaldehyde).

As for the aminotriazine-modified phenolic resin, that is, a compoundintramolecularly having a phenolic skeleton, a triazine ring, and aprimary amino group, a compound having a molecular structure obtained bycondensation reaction between a triazine compound, a phenol, and analdehyde is preferred because a cured product has high flame retardancy.

In view of the flame retardancy of a cured product, the other curingagent described above is preferably used such that the content ofphosphorus in the solid matter of the curable resin compositionaccording to the present invention is 1% to 9%.

If necessary, the curable resin composition of the present invention mayalso appropriately contain a curing accelerator. Various curingaccelerators can be used as the curing accelerator. Examples of thecuring accelerator include phosphorus compounds, tertiary amines,imidazole, metal salts of organic acids, Lewis acids, and amine complexsalts. In particular, when the curable resin composition is used as asemiconductor sealing material, a preferred phosphorus compound istriphenyl phosphine and a preferred amine compound is2-ethyl-4-methylimidazole in view of excellent curing properties, heatresistance, electric characteristics, moisture resistance reliability,and the like. The amount of the curing accelerator used is preferably0.01% to 1% by mass in the curable resin composition.

As described above, the curable resin composition of the presentinvention having been described so far in detail exhibits highsolubility in a solvent. Therefore, the curable resin compositionpreferably contains, in addition to the above-described components, anorganic solvent. Examples of the organic solvent that can be usedinclude methyl ethyl ketone, acetone, dimethylformamide, methyl isobutylketone, methoxy propanol, cyclohexanone, methyl cellosolve, ethyldiglycol acetate, and propylene glycol monomethyl ether acetate. Theselection of the solvent and the appropriate amount of the solvent usedcan be appropriately determined on the basis of the application. Forexample, in applications to printed wiring boards, alcohol organicsolvents or carbonyl group-containing organic solvents having a boilingpoint of 160° C. or less, such as methyl ethyl ketone, acetone, and1-methoxy-2-propanol are preferred and such organic solvents arepreferably used such that a nonvolatile content is 40% to 80% by mass.In applications to adhesive films for build-up, the organic solvent ispreferably a ketone such as acetone, methyl ethyl ketone, orcyclohexanone; an acetate such as ethyl acetate, butyl acetate,cellosolve acetate, propylene glycol monomethyl ether acetate, orcarbitol acetate; a carbitol such as cellosolve or butyl carbitol; anaromatic hydrocarbon such as toluene or xylene; or dimethylformamide,dimethylacetamide, N-methylpyrrolidone, or the like. In addition, theorganic solvent is preferably used such that a nonvolatile content is30% to 60% by mass.

To achieve flame retardancy, the curable resin composition may contain anon-halogen flame retardant that substantially contains no halogen atomsin the field of, for example, printed wiring boards as long asreliability is not degraded.

Examples of the non-halogen flame retardant include phosphorus flameretardants, nitrogen flame retardants, silicone flame retardants,inorganic flame retardants, and organic metal salt flame retardants. Useof these flame retardants is not limited at all. The flame retardantsmay be used alone, in combination of flame retardants of the same type,or in combination of flame retardants of different types.

Inorganic and organic flame retardants can be used as the phosphorusflame retardants. Examples of such inorganic compounds include redphosphorus and inorganic nitrogen-containing phosphorus compounds suchas ammonium phosphates (e.g., monoammonium phosphate, diammoniumphosphate, triammonium phosphate, and ammonium polyphosphate) andphosphoric acid amide.

The red phosphorus is preferably surface-treated in order to preventhydrolysis and the like. Examples of such a surface treatment methodinclude (i) a method of forming a coating with an inorganic compoundsuch as magnesium hydroxide, aluminum hydroxide, zinc hydroxide,titanium hydroxide, bismuth oxide, bismuth hydroxide, bismuth nitrate,or a mixture of the foregoing; (ii) a method of forming a coating with amixture of an inorganic compound such as magnesium hydroxide, aluminumhydroxide, zinc hydroxide, or titanium hydroxide, and a thermosettingresin such as a phenolic resin; and (iii) a method of forming a coatingwith a thermosetting resin such as a phenolic resin on a coating made ofan inorganic compound such as magnesium hydroxide, aluminum hydroxide,zinc hydroxide, or titanium hydroxide to provide double coatings.

Examples of the organic phosphorus compounds include, in addition togeneral-purpose organic phosphorus compounds such as phosphoric acidester compounds, phosphonic acid compounds, phosphinic acid compounds,phosphine oxide compounds, phosphorane compounds, and organicnitrogen-containing phosphorus compounds, cyclic organic phosphoruscompounds such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene=10-oxide,10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene=10-oxide, and10-(2,7-dihydroxynaphthyl)-10H-9-oxa-10-phosphaphenanthrene=10-oxide,and derivatives obtained by reactions between the cyclic organicphosphorus compounds and compounds such as epoxy resins and phenolicresins.

The amount of a phosphorus flame retardant added is appropriatelyselected on the basis of the type of the phosphorus flame retardant,other components in the curable resin composition, and a desired degreeof flame retardancy. For example, in 100 parts by mass of a curableresin composition containing all components such as an epoxy resin, acuring agent, a non-halogen flame retardant, a filler, and otheradditives, when red phosphorus is used as a non-halogen flame retardant,red phosphorus is preferably added in the range of 0.1 to 2.0 parts bymass. Similarly, when an organic phosphorus compound is used, theorganic phosphorus compound is preferably added in the range of 0.1 to10.0 parts by mass, particularly preferably, in the range of 0.5 to 6.0parts by mass.

When the phosphorus flame retardant is used, the phosphorus flameretardant may be used together with hydrotalcite, magnesium hydroxide,boride compounds, zirconium oxide, black dyes, calcium carbonate,zeolite, zinc molybdate, activated carbon, or the like.

Examples of the nitrogen flame retardants include triazine compounds,cyanuric acid compounds, isocyanuric acid compounds, and phenothiazine.Triazine compounds, cyanuric acid compounds, and isocyanuric acidcompounds are preferred.

Examples of the triazine compounds include melamine, acetoguanamine,benzoguanamine, melon, melam, succinoguanamine, ethylenedimelamine,melamine polyphosphate, and triguanamine; aminotriazine sulfatecompounds such as guanylmelamine sulfate, melem sulfate, and melamsulfate; the above-described aminotriazine-modified phenolic resin; andcompounds obtained by further modifying the aminotriazine-modifiedphenolic resin with tung oil, isomerized linseed oil, or the like.

Specific examples of the cyanuric acid compounds include cyanuric acidand melamine cyanurate.

The amount of such a nitrogen flame retardant added is appropriatelyselected on the basis of the type of the nitrogen flame retardant, othercomponents in the curable resin composition, and a desired degree offlame retardancy. For example, in 100 parts by mass of a curable resincomposition containing all components such as an epoxy resin, a curingagent, a non-halogen flame retardant, a filler, and other additives, thenitrogen flame retardant is preferably added in the range of 0.05 to 10parts by mass, particularly preferably, in the range of 0.1 to 5 partsby mass.

Such a nitrogen flame retardant may be used together with a metalhydroxide, a molybdenum compound, or the like.

The silicone flame retardants are not particularly limited as long asthe silicone flame retardants are organic compounds having siliconatoms. Examples of the silicone flame retardants include silicone oil,silicone rubber, and silicone resin.

The amount of such a silicone flame retardant added is appropriatelyselected on the basis of the type of the silicone flame retardant, othercomponents in the curable resin composition, and a desired degree offlame retardancy. For example, in 100 parts by mass of a curable resincomposition containing all components such as an epoxy resin, a curingagent, a non-halogen flame retardant, a filler, and other additives, thesilicone flame retardant is preferably added in the range of 0.05 to 20parts by mass. Such a silicone flame retardant may be used together witha molybdenum compound, alumina, or the like.

Examples of the inorganic flame retardants include metal hydroxides,metal oxides, metal carbonate compounds, metal powders, boron compounds,and low-melting glass.

Specific examples of the metal hydroxides include aluminum hydroxide,magnesium hydroxide, dolomite, hydrotalcite, calcium hydroxide, bariumhydroxide, and zirconium hydroxide.

Specific examples of the metal oxides include zinc molybdate, molybdenumtrioxide, zinc stannate, tin oxide, aluminum oxide, iron oxide, titaniumoxide, manganese oxide, zirconium oxide, zinc oxide, molybdenum oxide,cobalt oxide, bismuth oxide, chromium oxide, nickel oxide, copper oxide,and tungsten oxide.

Specific examples of the metal carbonate compounds include zinccarbonate, magnesium carbonate, calcium carbonate, barium carbonate,basic magnesium carbonate, aluminum carbonate, iron carbonate, cobaltcarbonate, and titanium carbonate.

Specific examples of the metal powders include powders of aluminum,iron, titanium, manganese, zinc, molybdenum, cobalt, bismuth, chromium,nickel, copper, tungsten, and tin.

Specific examples of the boron compounds include zinc borate, zincmetaborate, barium metaborate, boric acid, and borax.

Specific examples of the low-melting glass include CEEPREE (BokusuiBrown Co., Ltd.), hydrated glass SiO₂—MgO—H₂O, and glassy compounds ofPbO—B₂O₃, ZnO—P₂O₅—MgO, P₂O₅—B₂O₃—PbO—MgO, P—Sn—O—F, PbO—V₂O₅—TeO₂,Al₂O₃—H₂O, and lead borosilicate.

The amount of such an inorganic flame retardant added is appropriatelyselected on the basis of the type of the inorganic flame retardant,other components in the curable resin composition, and a desired degreeof flame retardancy. For example, in 100 parts by mass of a curableresin composition containing all components such as an epoxy resin, acuring agent, a non-halogen flame retardant, a filler, and otheradditives, the inorganic flame retardant is preferably added in therange of 0.05 to 20 parts by mass, particularly preferably, in the rangeof 0.5 to 15 parts by mass.

Examples of the organic metal salt flame retardants include ferrocene,acetylacetonato metal complexes, organic metal carbonyl compounds,organic cobalt salt compounds, organic metal sulfonates, and compoundsin which metal atoms and aromatic compounds or heterocyclic compoundsare bonded to each other through ionic bonds or coordinate bonds.

The amount of such an organic metal salt flame retardant added isappropriately selected on the basis of the type of the organic metalsalt flame retardant, other components in the curable resin composition,and a desired degree of flame retardancy. For example, in 100 parts bymass of a curable resin composition containing all components such as anepoxy resin, a curing agent, a non-halogen flame retardant, a filler,and other additives; the organic metal salt flame retardant ispreferably added in the range of 0.005 to 10 parts by mass.

The curable resin composition of the present invention may optionallycontain an inorganic filler. Examples of the inorganic filler includefused silica, crystalline silica, alumina, silicon nitride, and aluminumhydroxide. When the amount of such an inorganic filler added is madeparticularly large, fused silica is preferably used. The fused silicamay be used in the form of fragments or spheres. To increase the amountof fused silica added and to suppress an increase in the melt viscosityof the composition, fused silica in the form of spheres is preferablymainly used. To increase the amount of spherical silica added, the sizedistribution of silica particles is preferably appropriately adjusted.The filling factor of the filler is preferably high in view of flameretardancy and particularly preferably 20% by mass or more relative tothe whole amount of the curable resin composition. In applications toconductive paste and the like, a conductive filler such as silver powderor copper powder may be used.

The curable resin composition of the present invention may optionallycontain various additives such as a silane coupling agent, a releaseagent, a pigment, and an emulsifying agent.

The curable resin composition of the present invention can be obtainedby uniformly mixing the components above. The curable resin compositioncan be easily cured by a method similar to known methods. Examples ofsuch a cured product include formed cured products such as multilayerproducts, cast products, adhesive layers, coatings, and films.

Examples of applications of the curable resin composition according tothe present invention include printed wiring board materials, resincompositions for flexible wiring boards, interlayer insulating materialsfor build-up boards, semiconductor sealing materials, conductive pastes,adhesive films for build-up, resin casting materials, and adhesives.

Among these various applications, in the applications to insulatingmaterials for printed wiring boards and electronic circuit boards andadhesive films for build-up, the curable resin composition can be usedas insulating materials for boards within which passive components suchas capacitors and active components such as IC chips are embedded,so-called electronic-component built-in boards.

Among these, the curable resin composition has characteristics of highflame retardancy, high heat resistance, and solubility in a solvent andhence is preferably used for printed wiring board materials, resincompositions for flexible wiring boards, and interlayer insulatingmaterials for build-up boards. The curable resin composition isparticularly preferably used for printed circuit boards.

A printed circuit board of the present invention can be produced fromthe curable resin composition of the present invention by a method inwhich a curable resin composition that is in the form of varnish andcontains an epoxy resin, a phosphorus-containing oligomer, andfurthermore an organic solvent is impregnated into a reinforcing base; acopper foil is laminated on the reinforcing base; and the resultantlaminate is subjected to thermocompression bonding. Examples of thereinforcing base that can be used herein include paper, glass cloth,glass nonwoven fabric, aramid paper, aramid cloth, glass mat, and glassroving cloth. Such a method will be further described in detail. Thecurable resin composition in the form of varnish is heated to a heatingtemperature according to the type of a solvent used, preferably to 50°C. to 170° C., to provide a prepreg that is a cured product. The massratio of the resin composition and the reinforcing base that are usedherein is not particularly limited, but the mass ratio is generallypreferably adjusted such that the resin content in the prepreg is 20% to60% by mass. The thus-obtained prepreg is then stacked by a standardmethod, a copper foil is appropriately laminated thereon, and theresultant laminate is subjected to thermocompression bonding under apressure of 1 to 10 MPa at 170° C. to 250° C. for 10 minutes to 3 hours,whereby an intended printed circuit board can be provided.

A flexible wiring board is produced from the curable resin compositionof the present invention as follows. The phosphorus-containing oligomer,an epoxy resin, and an organic solvent and optionally another curingagent and a curing accelerator are mixed with each other and appliedonto an electrical insulating film with a coater such as a reverse rollcoater or a comma coater. The electrical insulating film is then heatedwith a heater at 60° C. to 170° C. for 1 to 15 minutes to evaporate thesolvent, whereby the adhesive composition is brought into the B-stage. Ametal foil is then bonded to the adhesive by thermocompression bondingwith a heating roll or the like. At this time, the compression bondingpressure is preferably 2 to 200 N/cm and the compression bondingtemperature is preferably 40° C. to 200° C. When sufficient bondingproperties are achieved at this time, this procedure may be finished.When complete curing is required, postcure is preferably furtherperformed at 100° C. to 200° C. for 1 to 24 hours. The adhesivecomposition film finally cured preferably has a thickness in the rangeof 5 to 100 μm.

An interlayer insulating material for build-up boards is produced fromthe curable resin composition of the present invention by, for example,the following method. The curable resin composition appropriatelycontaining rubber, a filler, and the like is applied onto a wiring boardin which circuits have been formed by a spray coating method, a curtaincoating method, or the like and is subsequently cured. Holes are thenoptionally made in predetermined through-hole portions and the like. Theboard is treated with a roughening agent and the surface thereof isrinsed with hot water to form irregularities. The board is plated with ametal such as copper. The plating method is preferably electrolessplating or electrolytic plating. Examples of the roughening agentinclude an oxidizing agent, an alkali, and an organic solvent. Such aprocedure is sequentially repeated as needed to alternately build up aresin insulating layer and a conductor layer having a predeterminedcircuit pattern. As a result, a build-up board can be provided. Notethat holes are made in the through-hole portions after the formation ofa resin insulating layer serving as an outermost layer. Alternatively, abuild-up board can be produced without the plating process as follows: acopper foil with a resin in which the resin composition has beensemi-cured on the copper foil is bonded to a wiring board in whichcircuits have been formed by thermocompression bonding at 170° C. to250° C., whereby a roughened surface is formed.

An adhesive film for build-up is produced from the curable resincomposition of the present invention by, for example, a method in whichthe curable resin composition of the present invention is applied onto asupport film to form a resin composition layer, whereby an adhesive filmfor multilayer printed wiring boards is provided.

When the curable resin composition of the present invention is used foran adhesive film for build-up, it is important that the adhesive filmsoftens under a lamination temperature condition (generally 70° C. to140° C.) in a vacuum lamination method and exhibits liquidity (resinflow) with which via holes or through-holes in a circuit board can befilled with the resin at the same time as lamination of the circuitboard. The above-described components are preferably mixed with eachother so that such characteristics are exhibited.

Herein, through-holes in multilayer printed wiring boards generally havea diameter of 0.1 to 0.5 mm and a depth of 0.1 to 1.2 mm, and it ispreferable that through-holes satisfying these ranges can be filled withthe resin. Note that, when lamination is performed on both surfaces of acircuit board, through-holes are desirably filled to about half of thethrough-holes.

Specifically, the above-described method for producing an adhesive filmcan be performed as follows. The curable resin composition in the formof varnish according to the present invention is prepared. The varnishcomposition is then applied onto a surface of a support film and theorganic solvent is subsequently removed by heating, hot-air blowing, orthe like to form a layer (α) of the curable resin composition.

The formed layer (α) generally has a thickness equal to or larger thanthe thickness of a conductor layer. Since a circuit board generally hasa conductor layer with a thickness in the range of 5 to 70 μm, the resincomposition layer preferably has a thickness of 10 to 100 μm.

Note that the layer (α) may be covered with a protective film describedbelow. By protecting the surface of the resin composition layer with aprotective film, adhesion of dust or the like to the surface andscratching formed on the surface can be prevented.

The support film and the protective film may be composed of, forexample, a polyolefin such as polyethylene, polypropylene, or polyvinylchloride; a polyester such as polyethylene terephthalate (hereinafter,sometimes abbreviated as “PET”) or polyethylene naphthalate;polycarbonate; polyimide; release paper; or a metal foil such as copperfoil or aluminum foil. Note that the support film and the protectivefilm may be subjected to a mat treatment, a corona treatment, and arelease treatment.

The thickness of the support film is not particularly limited and isgenerally 10 to 150 μm and preferably 25 to 50 μm. The thickness of theprotective film is preferably 1 to 40 μm.

The above-described support film is detached after the lamination isperformed on a circuit board or after an insulating layer is formed byheat-curing. By detaching the support film after the adhesion film isheat-cured, adhesion of dust or the like in the curing step can beprevented. When the support film is detached after the curing, thesupport film is generally subjected to a release treatment in advance.

A method for producing a multilayer printed wiring board with thethus-obtained adhesive film is performed by, for example, in the casewhere the layer (α) is protected with a protective film, removing theprotective film and performing lamination such that the layer (α) is indirect contact with a single surface or both surfaces of a circuit boardby, for example, a vacuum lamination method. The lamination may beperformed by a batch process or a continuous process with rolls. Theadhesive film and the circuit board may be optionally heated (preheated)before the lamination.

As for the lamination conditions, lamination is preferably performed ata compression bonding temperature (lamination temperature) of 70° C. to140° C., at a compression bonding pressure of 1 to 11 kgf/cm² (9.8×10⁴to 107.9×10⁴ N/m²), and under a reduced air pressure of 20 mmHg (26.7hPa) or less.

When the curable resin composition of the present invention is used as aconductive paste, for example, there are a method in which fineconductive particles are dispersed in the curable resin composition toprovide a composition for an anisotropic conductive film and a method inwhich the curable resin composition is turned into a resin compositionpaste for circuit connection or an anisotropic conductive adhesive, theresin composition paste and the anisotropic conductive adhesive being ina liquid state at room temperature.

In the preparation of a semiconductor sealing material from the curableresin composition of the present invention, an epoxy resin compositionprepared for semiconductor sealing materials can be produced bysufficiently melt-mixing the epoxy resin, the phosphorus-containingoligomer, the curing accelerator, and optionally another epoxy resincuring agent, and additives such as an inorganic filler optionally usingan extruder, a kneader, a roll, or the like until uniform mixing isachieved. At this time, the inorganic filler is generally silica. Thefilling factor of the inorganic filler is preferably in the range of 30%to 95% by mass relative to 100 parts by mass of the epoxy resincomposition; particularly preferably 70 parts by mass or more to improveflame retardancy, moisture resistance, and resistance to solder crackingand to decrease linear expansion coefficient; and more preferably 80parts by mass or more to considerably improve the advantages. As forsemiconductor package forming, there is a method in which thecomposition is formed by casting or with a transfer molding apparatus,an injection molding apparatus, or the like and then heated at 50° C. to200° C. for 2 to 10 hours to provide formed products serving assemiconductor devices.

The method for providing the cured product of the present invention maybe performed in conformity with a typical method for curing a curableresin composition. For example, the heating temperature may beappropriately selected in accordance with the types of curing agentscombined or the applications. In general, the composition obtained bythe above method may be heated at about 20° C. to 250° C.

Accordingly, by using the phosphorus-containing oligomer, the solubilityin a solvent is considerably improved compared with existingphosphorus-modified phenolic resins; and, in the form of a curedproduct, flame retardancy, heat resistance, and heat resistancereliability can be exhibited and applications to the most advancedprinted wiring board materials can be achieved. In addition, thephenolic resin can be efficiently and readily produced by the productionmethod of the present invention and molecular design according to thedegree of the intended properties can be performed.

EXAMPLES

The present invention will now be specifically described based onExamples and Comparative Examples. Note that melt viscosity at 180° C.,softening point, the content of phosphorus, GPC measurement, NMR, and MSspectrum were measured under the following conditions.

1) Melt viscosity at 180° C.: conformity with ASTM D4287

2) Softening-point measurement method: JIS K7234

3) Method for measuring the content of phosphorus: conformity with JISK0102-46

4) GPC: the measurement conditions are as follows.

Measurement apparatus: “HLC-8220 GPC” manufactured by Tosoh Corporation

Columns: guard column “HXL-L” manufactured by Tosoh Corporation,

+“TSK-GEL G2000HXL” manufactured by Tosoh Corporation,

+“TSK-GEL G2000HXL” manufactured by Tosoh Corporation,

+“TSK-GEL G3000HXL” manufactured by Tosoh Corporation,

+“TSK-GEL G4000HXL”, manufactured by Tosoh Corporation

Detector: RI (differential refractive refractometer)

Data processing: “GPC-8020 Model II version 4.10” manufactured by TosohCorporation

Measurement conditions: column temperature 40° C. developing solventtetrahydrofuran flow rate 1.0 ml/min

Standards: the following monodisperse polystyrenes whose molecularweights are known were used in accordance with the measurement manual ofthe “GPC-8020 Model II version 4.10”

(Used Polystyrenes)

“A-500” manufactured by Tosoh Corporation

“A-1000” manufactured by Tosoh Corporation

“A-2500” manufactured by Tosoh Corporation

“A-5000” manufactured by Tosoh Corporation

“F-1” manufactured by Tosoh Corporation

“F-2” manufactured by Tosoh Corporation

“F-4” manufactured by Tosoh Corporation

“F-10” manufactured by Tosoh Corporation

“F-20” manufactured by Tosoh Corporation

“F-40” manufactured by Tosoh Corporation

“F-80” manufactured by Tosoh Corporation

“F-128” manufactured by Tosoh Corporation

Samples: solutions (50 μl) obtained by filtrating a 1.0 mass %tetrahydrofuran solution in terms of resin solid matter through amicro-filter.

5) NMR: JNM-ECA500 nuclear magnetic resonance apparatus manufactured byJEOL Ltd.

Magnetic field strength: 500 MHz

Pulse width: 3.25 μsec

Number of acquisitions: 8000

Solvent: DMSO-d6

Sample concentration: 30 mass %

6) MS: AXIMA-TOF2 manufactured by SHIMADZU BIOTECH

Measurement mode: linear

Number of acquisitions: 50

Sample composition: sample/DHBA/NaTFA/THF=9.4 mg/104.7 mg/6.3 mg/1 ml

The content of components whose number of repeating units in thestructural formula (1) is 2 or more (hereinafter abbreviated as n=2 ormore) was calculated based on a peak area before 36.0 minutes in a GPCchart.

Example 1 Synthesis of phosphorus-containing oligomer (A-1)

A flask equipped with a thermometer, a cooling tube, a fractionaldistillation column, a nitrogen-gas inlet tube, and a stirrer wascharged with 122 g (1.0 mol) of 2-hydroxybenzaldehyde, 151.2 g (0.7 mol)of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (hereinafter,abbreviated as “HCA”), and 2.23 g (0.019 mol) of oxalic acid. Themixture was heated to 120° C. to allow the reaction to proceed for onehour: Subsequently, 172.8 g (0.8 mol) of HCA was added to the flask, andthe mixture was heated to 180° C. to allow the reaction to proceed forthree hours. Water was then removed under heating and reduced pressureto obtain 410 g of a phosphorus-containing oligomer (A-1) having astructural unit represented by structural formula below.

The obtained phosphorus-containing oligomer had a softening point of138° C. (B&R method), a melt viscosity (measurement method: ICIviscometer method, measurement temperature: 180° C.) of 66 dPa·s, ahydroxyl equivalent of 428 g/eq, and a phosphorus content of 10.5%. Thecontent of a component whose n=1 was 51%, the content of a componentwhose n=2 was 29.6%, and the content of components whose n=3 or more was19.4% (the content of components whose n=2 or more was 49.0%). FIG. 1shows a GPC chart of the obtained phosphorus-containing oligomer. FIG. 2shows a ¹³C-NMR chart of the obtained phosphorus-containing oligomer.FIG. 3 shows an MS spectrum of the obtained phosphorus-containingoligomer.

Example 2 Synthesis of Phosphorus-Containing Oligomer (A-2)

A flask equipped with a thermometer, a cooling tube, a fractionaldistillation column, a nitrogen-gas inlet tube, and a stirrer wascharged with 122 g (1.0 mol) of o-hydroxybenzaldehyde, 108 g (0.5 mol)of HCA, and 2.23 g (0.019 mol) of oxalic acid. The mixture was heated to120° C. to allow the reaction to proceed for one hour. Subsequently, 216g (1.0 mol) of HCA was added to the flask, and the mixture was heated to180° C. to allow the reaction to proceed for three hours. Water was thenremoved under heating and reduced pressure to obtain 415 g of aphosphorus-containing oligomer (A-2) having a structural unitrepresented by structural formula below.

The obtained phosphorus-containing oligomer had a softening point of130° C. (B&R method), a melt viscosity (measurement method: ICIviscometer method, measurement temperature: 180° C.) of 72 dPa·s, ahydroxyl equivalent of 430 g/eq, and a phosphorus content of 10.5 mass%. The content of a component whose n=1 was 55.3%, the content of acomponent whose n=2 was 26.0%, and the content of components whose n=3or more was 18.7% (the content of components whose n=2 or more was44.7%). FIG. 4 shows a GPC chart of the obtained phenolic resin.

Example 3 Synthesis of Phosphorus-Containing Oligomer (A-3)

A flask equipped with a thermometer, a cooling tube, a fractionaldistillation column, a nitrogen-gas inlet tube, and a stirrer wascharged with 122 g (1.0 mol) of o-hydroxybenzaldehyde, 129.6 g (0.6 mol)of HCA, and 3.81 g (0.032 mol) of oxalic acid. The mixture was heated to120° C. to allow the reaction to proceed for one hour. Subsequently,129.6 g (0.6 mol) of HCA was added to the flask, and the mixture washeated to 180° C. to allow the reaction to proceed for three hours.Water was then removed under heating and reduced pressure to obtain 415g of a phosphorus-containing oligomer (A-3) having a structural unitrepresented by structural formula below.

The obtained phosphorus-containing oligomer had a softening point of150° C. (B&R method), a melt viscosity (measurement method: ICIviscometer method, measurement temperature: 180° C.) of 105 dPa·s, ahydroxyl equivalent of 363.2 g/eq, and a phosphorus content of 9.9 mass%. The content of a component whose n=1 was 33.8%, the content of acomponent whose n=2 was 31.2%, and the content of components whose n=3or more was 35.0% (the content of components whose n=2 or more was66.2%). FIG. 5 shows a GPC chart of the obtained phenolic resin.

Example 4 Synthesis of Phenolic Resin (A-4)

A flask equipped with a thermometer, a cooling tube, a fractionaldistillation column, a nitrogen-gas inlet tube, and a stirrer wascharged with 122 g (1.0 mol) of o-hydroxybenzaldehyde, 129.6 g (0.6 mol)of HCA, and 5.54 g (0.047 mol) of oxalic acid. The mixture was heated to120° C. to allow the reaction to proceed for two hours. Subsequently,129.6 g (0.6 mol) of HCA was added to the flask, and the mixture washeated to 180° C. to allow the reaction to proceed for one hour.Furthermore, 172.8 g (0.8 mol) of HCA was added to the flask to allowthe reaction to proceed at 180° C. for two hours. Water was then removedunder heating and reduced pressure to obtain 504 g of a phenolic resin(A-4) having a structural unit represented by structural formula below.

The obtained phenolic resin had a softening point of 142° C. (B&Rmethod), a melt viscosity (measurement method: ICI viscometer method,measurement temperature: 180° C.) of 73 dPa·s, a hydroxyl equivalent of536 g/eq, and a phosphorus content of 11.2 mass %. The content of acomponent whose n=1 was 43.9%, the content of a component whose n=2 was30.1%, and the content of components whose n=3 or more was 26.0% (thecontent of components whose n=2 or more was 56.1%). FIG. 6 shows a GPCchart of the obtained phenolic resin.

Example 5 Synthesis of Phenolic Resin (A-5)

A flask equipped with a thermometer, a cooling tube, a fractionaldistillation column, a nitrogen-gas inlet tube, and a stirrer wascharged with 122 g (1.0 mol) of o-hydroxybenzaldehyde, 10.8 g (0.05 mol)of HCA, and 5.54 g (0.047 mol) of oxalic acid. The mixture was heated to120° C. to allow the reaction to proceed for two hours. Subsequently,313.2 g (1.45 mol) of HCA was added to the flask, and the mixture washeated to 180° C. to allow the reaction to proceed for three hours.Water was then removed under heating and reduced pressure to obtain 415g of a phenolic resin (A-5) having a structural unit represented bystructural formula below.

The obtained phenolic resin had a softening point of 84° C. (B&Rmethod), a melt viscosity (measurement method: ICI viscometer method,measurement temperature: 150° C.) of 1.0 dPa·s, a hydroxyl equivalent of420 g/eq, and a phosphorus content of 10.5%. The content of a componentwhose n=1 was 86.7%, the content of a component whose n=2 was 9.9%, andthe content of components whose n=3 or more was 3.4% (the content ofcomponents whose n=2 or more was 13.3%). FIG. 7 shows a GPC chart of theobtained phenolic resin.

Synthetic Comparative Example 1 Synthesis of Phenolic Compound (A-6)(the Compound Disclosed in PTL 2)

A flask equipped with a thermometer, a cooling tube, a fractionaldistillation column, a nitrogen-gas inlet tube, and a stirrer wascharged with 122 g (1.0 mol) of p-hydroxybenzaldehyde, 216 g (1.0 mol)of HCA, and 336 g of 2-propanol. The mixture was refluxed for five hoursto precipitate a white solid. The white solid was then filtered, washedwith 1000 mL of 2-propanol, and dried to obtain 325 g (yield: 96%) of aphenolic compound (A-6) having a structure represented by structuralformula below.

FIG. 7 shows a GPC chart of the obtained phenolic compound.

Synthetic Comparative Example 2 Synthesis of Phenolic Resin (A-7) (theCompound Disclosed in NPL 3)

A flask equipped with a thermometer, a cooling tube, a fractionaldistillation column, a nitrogen-gas inlet tube, and a stirrer wascharged with 236.6 g (0.7 mol) of the phenolic compound (A-6) obtainedin Synthetic Comparative Example 1 and 3.08 g (0.034 mol) of oxalicacid. The mixture was heated under stirring at 180° C. for three hours.Water was then removed under heating and reduced pressure to obtain 210g of a phenolic resin (A-7) mainly having a structural unit representedby structural formula below.

The obtained phenolic resin had a softening point of 84° C. (B&Rmethod), a melt viscosity (measurement method: ICI viscometer method,measurement temperature: 150° C.) of 1.0 dPa·s, a hydroxyl equivalent of420 g/eq, and a phosphorus content of 9.4 mass %. The content ofcomponents whose n=2 or more was 34.0%. FIG. 8 shows a GPC chart of theobtained phenolic resin (A-7).

Synthetic Comparative Example 3 Synthesis of Phenolic Compound (A-8)(the Compound Disclosed in PTL 4)

A flask equipped with a thermometer, a cooling tube, a fractionaldistillation column, a nitrogen-gas inlet tube, and a stirrer wascharged with 169 g (0.5 mol) of the phenolic compound (A-6) obtained inSynthetic Comparative Example 1, 47 g (0.5 mol) of phenol, and 1.25 g ofp-toluene sulfonic acid. The mixture was heated to 180° C. to allow thereaction to proceed at 180° C. for eight hours. The reaction product wasthen filtered and dried to obtain 199 g of a phenolic compound (A-8)represented by structural formula below.

The melting point of the obtained phenolic compound (A-7) was 286° C.FIG. 9 shows a GPC chart of the obtained phenolic compound (A-8).

Examples 6 to 10 and Comparative Examples 1 and 2 (Test for Solubilityin Solvent)

Each of the phosphorus-containing oligomers (A-1) to (A-5), the phenolicresin (A-7), and the phenolic compound (A-8) was inserted into ascrew-capped sample bottle in an amount of 50 g, and then each oforganic solvents was added thereto in such an amount that thepredetermined concentrations shown in Table 1 below were achieved. Afterthe mixture was stirred with a shaker at room temperature, the state ofthe solvent in the bottle was confirmed through visual inspection.Herein, a uniformly transparent state was defined as a state of“dissolved”, and a state in which a solid component was precipitated ordeposited was defined as a state of “not dissolved”.

TABLE 1 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 C. E. 1 C. E. 2 SolventConcentration A-1 A-2 A-3 A-4 A-5 A-7 A-8 Methyl ethyl 50 mass % not notnot not not not not ketone dissolved dissolved dissolved dissolveddissolved dissolved dissolved 60 mass % dissolved dissolved dissolveddissolved dissolved not not dissolved dissolved 70 mass % dissolveddissolved dissolved dissolved dissolved not not dissolved dissolved1-methoxy- 50 mass % dissolved dissolved dissolved dissolved dissolvednot not 2-propanol dissolved dissolved 60 mass % dissolved dissolveddissolved dissolved dissolved not not dissolved dissolved 70 mass %dissolved dissolved dissolved dissolved dissolved not not dissolveddissolved Ex.: Example C.E.: Comparative Example

(The abbreviations “A-1” to “A-8” in Table 1 denote the correspondingphosphorus-containing oligomers, phenolic resin, and phenolic compound.)

Examples 11 and 12 and Comparative Examples 3 to 6

Epoxy resin compositions were prepared in accordance with formulationsshown in Table 2 by a method described below and then cured under theconditions below to experimentally produce multilayer plates. Themultilayer plates were subjected to various evaluations. Table 2 showsthe results.

[Preparation of Epoxy Resin Composition]

Epoxy resins, curing agents, and other components were mixed inaccordance with the formulations shown in Table 2, and then compositionswere prepared so as to finally have a non-volatile content (N.V.) of 58mass %.

[Conditions for Producing Multilayer Plate]

Base: 100 μm; glass cloth “#2116” manufactured by Nitto Boseki Co., Ltd.

Number of plies: 6

Conditions for forming prepreg: 160° C./2 min

Copper foil: 18 μm; JTC foil manufactured by Nippon Mining & Metals Co.,Ltd.

Curing conditions: 200° C., 40 kg/cm², 1.5 hours

Thickness of formed plate: 0.8 mm

[Physical Property Test Conditions]

Glass transition temperature: measured by a TMA method (compressivestress method) after an etching treatment was performed to remove acopper foil. Temperature increase rate: 10° C./min

Combustion test: the test method was in conformity with a UL-94 verticaltest.

Thermal delamination test (T288 test): evaluation for thermaldelamination resistance (with copper foil) at 288° C. was performed inconformity with IPC TM650.

TABLE 2 Example Comparative Example 11 12 3 4 5 6 Epoxy resin N-690 5354 67 34 40 FX-289BEK75 76 Curing agent A-1 27 27 A-2 A-7 66 A-8 60TD-2090 20 19 33 24 Curing 2E4MZ (weight %) 0.1 0.1 0.1 0.1 0.1 0.1accelerator Organic solvent MEK 72.4 72.4 72.4 72.4 72.4 72.4 Glasstransition temperature (TMA) 150 146 183 Not Not 129 (° C.) evaluatedevaluated Thermal delamination test (T288 >120 >120 >120 due to due to 0test) crystal crystal Flame Total combustion 28 32 — precipitationprecipitation 45 retardancy time (second) Combustion test V-0 V-0Combustion V-0 class

The abbreviations in Table 2 are as follows. N-690: cresol novolac epoxyresin (“EPICLON N-690”, epoxy equivalent: 215 g/eq) manufactured by DICCorporation FX-289BEK75: phosphorus-modified epoxy resin (“FX-289BEK75”,manufactured by Tohto Kasei Co., Ltd.: epoxy resin obtained through areaction between a cresol novolac epoxy resin and9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, epoxy equivalent:330 g/eq, and phosphorus content: 3.0 mass %)

A-1: phosphorus-containing oligomer (A-1) obtained in Example 1

A-2: phosphorus-containing oligomer (A-2) obtained in Example 2

A-7: phenolic resin (A-7) obtained in Synthetic Comparative Example 2

A-8: phenolic compound (A-8) obtained in Synthetic Comparative Example 3

TD-2090: phenolic novolac phenolic resin (“TD-2090”, manufactured by DICCorporation, hydroxyl equivalent: 105 g/eq)

2E4MZ: 2-ethyl-4-methylimidazole

The invention claimed is:
 1. A phosphorus-containing oligomercomposition represented by structural formula (1) below

(in the formula, R¹ represents a hydrogen atom, an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or aphenyl group; n is the number of repeating units and an integer of 1 ormore; X is a structural unit represented by structural formula (x1)below;

Y is a hydrogen atom, a hydroxyl group, or a structural unit representedby the structural formula (x1); and, in the structural formula (x1), R²,R³, R⁴, and R⁵ each independently represent a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, a phenyl group, or an aralkyl group),wherein the phosphorus-containing oligomer composition is a mixture of aphosphorus-containing compound whose n is 1 in the structural formula(1) and phosphorus-containing oligomers whose n is 2 or more in thestructural formula (1), and the content of the phosphorus-containingoligomers whose n is 2 or more in the structural formula (1) is in therange of 5% to 90% in terms of peak area in GPC measurement.
 2. Acurable resin composition being a thermosetting resin composition thatcomprises an epoxy resin and a curing agent as essential components,wherein the phosphorus-containing oligomer composition according toclaim 1 is used as the curing agent.
 3. A cured product obtained bycuring the curable resin composition according to claim
 2. 4. A printedwiring board obtained by further adding an organic solvent to thecurable resin composition according to claim 2 to form a resincomposition in the form of varnish, impregnating a reinforcing base withthe resin composition in the form of varnish, laminating a copper foilon the reinforcing base, and performing thermocompression bonding. 5.The phosphorus-containing oligomer composition according to claim 1,wherein the phosphorus-containing oligomer composition has a phosphoruscontent of 9% to 12% by mass.
 6. A curable resin composition being athermosetting resin composition that comprises an epoxy resin and acuring agent as essential components, wherein the phosphorus-containingoligomer composition according to claim 5 is used as the curing agent.7. A cured product obtained by curing the curable resin compositionaccording to claim
 6. 8. A printed wiring board obtained by furtheradding an organic solvent to the curable resin composition according toclaim 6 to form a resin composition in the form of varnish, impregnatinga reinforcing base with the resin composition in the form of varnish,laminating a copper foil on the reinforcing base, and performingthermocompression bonding.
 9. The phosphorus-containing oligomercomposition according to claim 1, wherein the phosphorus-containingoligomer composition is obtained through a reaction between a compound(a1) represented by structural formula (a1-1) below

(in the formula, R², R³, R⁴, and R⁵ each independently represent ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenylgroup, or an aralkyl group) and a compound (a2) represented bystructural formula (a2) below

(in the formula, R¹ represents a hydrogen atom, an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or aphenyl group).
 10. A curable resin composition being a thermosettingresin composition that comprises an epoxy resin and a curing agent asessential components, wherein the phosphorus-containing oligomercomposition according to claim 9 is used as the curing agent.
 11. Acured product obtained by curing the curable resin composition accordingto claim
 10. 12. A printed wiring board obtained by further adding anorganic solvent to the curable resin composition according to claim 10to form a resin composition in the form of varnish, impregnating areinforcing base with the resin composition in the form of varnish,laminating a copper foil on the reinforcing base, and performingthermocompression bonding.